Reactor seal incorporating a pivotal orifice member



y 3, 1959 N. R. St LAURENT 3,453,987

REACTOR SEAL INCORPORATING A PIVQTAL ORIFICE MEMBER Filed Feb. 27, 1968 FIG.

F I a a I a A. a

1 NVENTOR NMAN R. s'r. LAURENT Z ya ATTORNEY United States Patent 3,453,987 REACTOR SEAL INCORPORATING A PIVOTAL ORIFICE MEMBER Norman R. St. Laurent, Southwick, Mass., assignor to United Aircraft Corporation, East Hartford. Conn., a corporation of Delaware Filed Feb. 27, 1968, Ser. No. 708,651 Int. Cl. C23c 13/02 US. Cl. 118-48 2 Claims ABSTRACT OF THE DISCLOSURE In apparatus wherein a moving Wire is drawn through a reaction tube and a material is deposited thereon, a reactor seal is provided to isolate the reactant gases within the tube from the surrounding atmosphere. The reactor seal comprises an orificed fitting containing a well or pool of liquid metal through which the wire is drawn, the liquid metal being held in the fitting at the orifice by surface tension forces. The orifice is established as a narrow slit in a thin plate, the plate being pivotally mounted in the fitting so that it may be raised and lowered out of and into the opening in the fitting through which the wire is drawn.

Background 0 the invention The invention herein described was made in the course of a contract with the United States Air Force.

The present invention relates in general to scaling devices and, more particularly, to reactor seals incorporating a liquid sealant.

It is known that filamentary materials may be conveniently produced by pyrolytic techniques wherein the desired material is deposited on a resistively heated wire which is drawn through a reactant mixture containing the material in vapor form. One such technique is disclosed in a copending application, Ser. No. 618,512, entitled Process for Forming Stoichiometric Silicon Carbide Coatings and Filaments by Malcolm Basche and Urban E. Kuntz, which shares a common assignee with the present invention. According to these methods, the wire upon which deposition is desired is introduced to and exits from a tubular reactor through a fitting provided at each end thereof, each fitting being fabricated to retain a pool of liquid sealant, such as a liquid metal. The liquid metal, typically mercury, normally performs a dual function. It prevents the escape of the reactant gases along the wire as the wire is rapidly drawn through the reactor and, further, affords convenient means for establishing electrical contact with the wire for resistance heating purposes.

The mercury is normally retained at or in the fitting through surface tension forces. To accomplish this end, the fitting is orificed to provide an opening through which the wire may freely pass but which is small enough to, in combination with the wire, retain the mercury at the fitting by means of surface tension. The orifice has normally been established in the past by drilling a hole of the appropriate diameter in the fitting or in a jewel which is attached to the fitting. However, threading of the wire through fine holes of this nature, typically 3-20 mils in diameter, requires disassembly of the reactor and is accordingly accomplished only with considerable difficulty. In some cases, the disassembly procedure mut be carefully conducted to avoid operator exposure to toxic, corrosive, or combustible materials.

Summary of the invention In accordance with the present invention a reactor seal is provided in which a pivotally mounted, slotted plate acts as the orifice-forming member in the passageway in the seal through which the wire is drawn. The pivoted plate is attached to the seal in such fashion that it may be raised to completely expose the entire cross-sectional area of the passageway for ease of threading of a filament through the seal, and it may be lowered to seal the opening and retain the mercury in the seal by means of surface tension. Because the diameter of the passageway in the seal is no longer critical as to size since the slit establishes the orifice, threading of the wire therethrough is readily accomplished, Further, because the frequency of disassembly of the reaction apparatus is reduced, exposure to the sometimes toxic, corrosive or combustible reactant gases is minimized.

Brief description of the drawings FIGURE 1 is a view, taken in cross section, of a typical reactor seal incorporating the teachings of the present invention;

FIGURE 2 is a top view of the seal. of FIGURE 1, not including the sealant, which illustrates particularly the construction of the slotted orifice plate and its location with respect to the filament transiting the fitting.

Descripion 0 the preferred embodiments Referring to FIGURES 1 and 2, the reactor seal in the embodiment shown may be seen to comprise an end fitting 2 which is usually formed of a metal in those instances Where it is to be utilized to establish electrical contact with the wire being processed. The seal is provided with a passageway 6 therethrough through which a 'Wire 8 exits from the reactor, this passageway normally being axially aligned with the wire and sized to permit the wire to be readily threaded therethrough.

A slotted plate 10 is attached to the top of the fitting at a hinge connection 12, the distal end of the slotted plate being movable through an angle of about Accordingly, in its lowered position the plate seals the passageway -6 through the fitting except for the slot forming the orifice 16. In a raised position, the plate is rotated out of the passageway increasing its effective cross-sectional area to facilitate the threading operation. The plate 10 is preferably formed so that the slit opening 16 at its open end is in the form of a wide V for ease in threading of the wire. Accordingly, after the filament is threaded through the reactor, the plate is lowered to position the wire in the slit and the mercury is added so that the seal is formed about the wire. The slit, which may be formed to a typical width of 3-15 mils, will be made large enough so that the wire may readily pass therethrough but small enough so that the mercury or other sealant will be retained atop the plate by means of surface tension. For rethreading, the plate may be raised to an open position by means of a rod inserted through the passage-way 6, or through the use of other suitable means.

During the threading operation, it is, of course, desirable to lift the slotted plate 10 to take advantage of the full diameter of the passageway 6. In this upright position the orifice is effectively removed from the seal so that the mercury will not be held in the seal and must be removed. For this purpose a fill tube 20 is provided through which mercury can be added to and removed from the system and through while the mercury level may be maintained.

The seal is adapted to fit closely within the tubular member 22 which forms the reaction chamber and leakage of gas between the tube and fitting is prevented by the mercury which sits in contact with the tube 22. It is, of course, possible to form a well in the fitting in which the mercury is contained and to provide the seal between the fitting and the reaction tube in some other manner.

While the invention has been described in connection with a particular preferred embodiment, no limitation is intended and numerous modifications thereto will be evi- 3 dent to those skilled in the art within the true spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. In a vertically arranged reactor vessel wherein a vapor deposition is effected on a moving substrate, a reactor seal comprising:

a liquid sealant comprising a pool of mercury disposed at an end of the vessel and through which the substrate moves;

an end fitting forming an end closure for the reactor vessel, the fitting having a vertically disposed passageway therethrough through which the substrate is drawn, and the fitting supporting said liquid seal; and

said fitting including a horizontally disposed plate, pivotally mounted on the inner surface structure thereof and movable to open and close the passageway;

the distal end of the plate having a narrow slot formed therein, the slot being wide enough to provide free passage of the substrate therethrough but narrow enough to retain said liquid sealant thereon. 2. The reactor seal of claim 1 in which the slit is formed to a width of 3-15 mils.

References Cited UNITED STATES PATENTS Bassett et al. 118-405 Lodge 118-405 Otto 118-405 X Denham 118405 Van der Linden et al. 118-47 X Robbins 11849.5

MORRIS KAPLAN, Primary Examiner. 

